In recent years, safe and clean natural renewable energy such as solar power generation and wind power generation has been introduced. However, the output of natural renewable energy is not stable, and the mass introduction may negatively affect the voltage and frequency of power systems. If the supply of natural renewable energy largely exceeds the power demand, the natural renewable energy power generation systems need to be stopped, resulting in reduced utilization of power generation facilities.
To solve such problems, a large-scale storage battery system using secondary batteries is added to the power generation systems, and is expected to prevent output fluctuations of the natural energy by charging/discharging power to and from the storage batteries, and to store surplus power in the storage batteries.
A storage battery system for power systems is used to prevent output fluctuations of natural renewable energy and to stabilize frequency in power systems. When a storage battery system is used for such purposes, the storage battery repeats charging and discharging constantly, and there is little time to stop the system. Conventionally, a current integration method has been used to estimate the state of charge (SOC) of a storage battery. However, using the storage battery in such a way so as to repeat charging and discharging constantly may cause current measurement errors to be accumulated and may not be able to estimate the SOC correctly, thus affecting the operation of the storage battery system.
More specifically, when an SOC estimation value is estimated smaller than the real value, the apparent dischargeable capacity becomes smaller. As a result, the storage battery system may not be able to operate efficiently. If the SOC estimation value is estimated larger than the real value, the storage battery may reach the end-of-discharge voltage (Vlower) before the SOC becomes 0%. As a result, the storage battery system may stop unexpectedly.
The present invention has been made in view of the above problem, and an object of the present invention is to correctly estimate the actual chargeable/dischargeable capacity even when a storage battery system repeats charging and discharging constantly, and to provide a storage battery management device, a method, and a computer program capable of stably operating the storage battery system.